In-situ curing of color conversion layer

ABSTRACT

A method of fabricating a multi-color display includes dispensing a photo-curable fluid that includes a color conversion agent over a display having a backplane and an array of light emitting diodes electrically integrated with backplane circuitry of the backplane, activating a plurality of light emitting diodes in the array of light emitting diodes to illuminate and cure the first photo-curable fluid to form a color conversion layer over each of the first plurality of light emitting diodes to convert light from the plurality of light emitting diodes to light of a first color, and removing an uncured remainder of the first photo-curable fluid. This process is repeated with a fluid having different color conversion components for another color.

TECHNICAL FIELD

This disclosure generally relates to fabrication of micro-LED displays.

BACKGROUND

A light emitting diode (LED) panel uses an array of LEDs, withindividual LEDs providing the individually controllable pixel elements.Such an LED panel can be used for a computer, touch panel device,personal digital assistant (PDA), cell phone, television monitor, andthe like.

An LED panel that uses micron-scale LEDs based on III-V semiconductortechnology (also called micro-LEDs) would have a variety of advantagesas compared to OLEDs, e.g., higher energy efficiency, brightness, andlifetime, as well as fewer material layers in the display stack whichcan simplify manufacturing. However, there are challenges to fabricationof micro-LED panels. Micro-LEDs having different color emission (e.g.,red, green and blue pixels) need to be fabricated on differentsubstrates through separate processes. Integration of the multiplecolors of micro-LED devices onto a single panel requires apick-and-place step to transfer the micro-LED devices from theiroriginal donor substrates to a destination substrate. This ofteninvolves modification of the LED structure or fabrication process, suchas introducing sacrificial layers to ease die release. In addition,stringent requirements on placement accuracy (e.g., less than 1 um)limit either the throughput, the final yield, or both.

An alternative approach to bypass the pick-and-place step is toselectively deposit color conversion agents (e.g., quantum dots,nanostructures, florescent materials or organic substances) at specificpixel locations on a substrate fabricated with monochrome LEDs. Themonochrome LEDs can generate relatively short wavelength light, e.g.,purple or blue light, and the color conversion agents can convert thisshort wavelength light into longer wavelength light, e.g., red or greenlight for red or green pixels. The selective deposition of the colorconversion agents can be performed using high-resolution shadow masks orcontrollable inkjet or aerosol jet printing.

SUMMARY

A method of fabricating a multi-color display includes dispensing afirst photo-curable fluid that includes a first color conversion agentover a display having a backplane and an array of light emitting diodeselectrically integrated with backplane circuitry of the backplane,activating a first plurality of light emitting diodes in the array oflight emitting diodes to illuminate and cure the first photo-curablefluid to form a first color conversion layer over each of the firstplurality of light emitting diodes to convert light from the firstplurality of light emitting diodes to light of a first color, removingan uncured remainder of the first photo-curable fluid, thereafterdispensing a second photo-curable fluid including a second colorconversion agent over the display, activating a second plurality oflight emitting diodes in the array of light emitting diodes toilluminate and cure the second photo-curable fluid to form a secondcolor conversion layer over each of the second plurality of lightemitting diodes to convert light from the second plurality of lightemitting diodes to light of a different second color, and removing anuncured remainder of the second photo-curable fluid.

Implementations may include one or more of the following features.

A third photo-curable fluid may be dispensed over the display. The thirdphoto-curable fluid may including a third color conversion agent. Athird plurality of light emitting diodes in the array of light emittingdiodes may be activated to illuminate and cure the third photo-curablefluid to form a third color conversion layer over each of the thirdplurality of light emitting diodes to convert light from the thirdplurality of light emitting diodes to light of a different third color.An uncured remainder of the third photo-curable fluid may be removed.

The light emitting diodes of the array of light emitting diodes may beconfigured to generate ultraviolet light. The first color, second colorand third color may be selected from blue, green and red. The firstcolor may be blue, the second color may be green, and the third colormay be red.

The array of light emitting diodes may include a third plurality oflight emitting diodes, and light emitting diodes of the array of lightemitting diodes may be configured to generate light of a different thirdcolor. No color conversion layer need be formed over the third pluralityof light emitting diodes. The light emitting diodes of the array oflight emitting diodes may be configured to generate blue or violetlight. The first color and second color may be selected from green andred. The first color may be green and the second color may be red.

Dispensing the first photo-curable fluid and dispensing the secondphoto-curable fluid may include one or more of a spin-on, dipping,spray-on, or inkjet process. Removing the uncured remainder of the firstphoto-curable fluid and the second photo-curable fluid may include oneor more of rinsing and dissolving.

A plurality of isolation walls may be formed on the backplane betweenadjacent light emitting diodes of the array of light emitting diodes.During activation of the first plurality of light emitting diodes, theisolation walls may block illumination from the first plurality of lightemitting diodes from reaching the second plurality of light emittingdiodes. The isolation walls may be formed of a photoresist.

At least one of the first photo-curable fluid and the secondphoto-curable fluid may include a solvent. The solvent may beevaporated. An ultraviolet blocking layer may be formed over the arrayof light emitting diodes.

Light emitting diodes of the array of light emitting diodes may be aremicro-LEDs.

In another aspect, a multi-color display includes a backplane havingbackplane circuitry, an array of micro-LEDs electrically integrated withbackplane circuitry of the backplane, a first color conversion layerover each of a first plurality of light emitting diodes, a second colorconversion layer over each of a second plurality of light emittingdiodes, and a plurality of isolation walls separating adjacentmicro-LEDs of the array. The micro-LEDs of the array are configured togenerate illumination of the same wavelength range, the first colorconversion layer converts the illumination to light of a first color,and the second color conversion layer converts the illumination to lightof a different second color.

Implementations can optionally provide (and are not limited to) one ormore of the following advantages.

The processing steps (coating, in-situ curing, and rinsing) supportlarge format and high-throughput operation. Thus, color conversionagents can be selectively formed over an array of micro-LEDs with higheryield and throughput. This may permit multi-color micro-LED displays tobe fabricated in a commercially viable manner. Flexible and/orstretchable displays can be fabricated more easily. In-situ curing canautomatically ensure alignment accuracy.

The host polymer can serve as a passivation layer for the protection. Itis also possible for the host polymer to provide other functions, e.g.,an optical functionality, when properly doped with functionalingredients.

Other aspects, features, and advantages will be apparent from thedescription and drawings, and from the claims.

A variety of implementations are described below. It is contemplatedthat elements and features of one implementation may be beneficiallyincorporated in other implementations without further recitation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic top view of a micro-LED array that has alreadybeen integrated with a backplane.

FIG. 2A is a schematic top view of a portion of a micro-LED array.

FIG. 2B is a schematic cross-sectional view of the portion of themicro-LED array from FIG. 2A.

FIGS. 3A-3H illustrate a method of selectively forming color conversionagent (CCA) layers over a micro-LED array.

FIGS. 4A-4C illustrate formulations of photo-curable fluid.

FIGS. 5A-5E illustrate a method of fabricating a micro-LED array andisolation walls on a backplane.

FIGS. 6A-6D illustrate another method of fabricating a micro-LED arrayand isolation walls on a backplane.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

As noted above, selective deposition of color conversion agents can beperformed using use high-resolution shadow masks or controllable inkjetor aerosol jet printing. Unfortunately, shadow masks are prone toproblems with alignment accuracy and scalability, whereas inkjet andaerosol jet techniques suffer from resolution (inkjet), accuracy(inkjet) and throughput (aerosol jet) problems. In order to manufacturemicro-LED displays, new techniques are needed to precisely andcost-effectively provide color conversion agents for different colorsonto different pixels on a substrate, such as a large area substrate orflexible substrate.

A technique that may address these problems is to coat a layer ofphoto-curable fluid containing a color conversion agent (CCA) for afirst color on a substrate having an array of monochrome micro-LEDs,then turn on selected LEDs to trigger in-situ polymerization andimmobilize the CCA in the vicinity of the selected subpixels. Theuncured fluid over the non-selected subpixels can be removed, and thenthe same process can be repeated with CCAs for different colors untilall subpixels on the wafer are covered with CCAs of the desired colors.This technique may overcome the challenges in alignment accuracy,throughput and scalability.

FIG. 1 illustrates a micro-LED display 10 that includes an array 12 ofindividual micro-LEDs 14 (see FIGS. 2A and 2B) disposed on a backplane16. The micro-LEDs 14 are already integrated with backplane circuitry 18so that each micro-LED 14 can be individually addressed. For example,the backplane circuitry 18 can include a TFT active matrix array with athin-film transistor and a storage capacitor (not illustrated) for eachmicro-LED, column address and row address lines 18 a, column and rowdrivers 18 b, etc., to drive the micro-LEDs 14. Alternatively, themicro-LEDs 14 can be driven by a passive matrix in the backplanecircuitry 18. The backplane 16 can be fabricated using conventional CMOSprocesses.

FIGS. 2A and 2B illustrate a portion 12 a of the micro-LED array 12 withthe individual micro-LEDs 14. All of the micro-LEDs 14 are fabricatedwith the same structure so as to generate the same wavelength range(this can be termed “monochrome” micro-LEDs). For example, themicro-LEDs 14 can generate light in the ultraviolet (UV), e.g., the nearultraviolet, range. For example, the micro-LEDs 14 can generate light ina range of 365 to 405 nm. As another example, the micro-LEDs 14 cangenerate light in the violet or blue range. The micro-LEDs can generatelight having a spectral bandwidth of 20 to 60 nm.

FIG. 2B illustrates a portion of the micro-LED array that can provide asingle pixel. Assuming the micro-LED display is a three-color display,each pixel includes three sub-pixels, one for each color, e.g., one eachfor the blue, green and red color channels. As such, the pixel caninclude three micro-LEDs 14 a, 14 b, 14 c. For example, the firstmicro-LED 14 a can correspond to a blue subpixel, the second micro-LED14 b can correspond to a green subpixel, and the third micro-LED 14 ccan correspond to a red subpixel. However, the techniques discussedbelow are applicable to micro-LED displays that use a larger number ofcolors, e.g., four or more colors. In this case, each pixel can includefour or more micro-LEDs, with each micro-LED corresponding to arespective color. In addition, the techniques discussed below areapplicable to micro-LED displays that use just two colors.

In general, the monochrome micro-LEDs 14 can generate light in awavelength range having a peak with a wavelength no greater than thewavelength of the highest-frequency color intended for the display,e.g., purple or blue light. The color conversion agents can convert thisshort wavelength light into longer wavelength light, e.g., red or greenlight for red or green subpixels. If the micro-LEDs generate UV light,then color conversion agents can be used to convert the UV light intoblue light for the blue subpixels.

Vertical isolation walls 20 are formed between neighboring micro-LEDs.The isolation walls provide for optical isolation to help localizepolymerization and reduce optical crosstalk during the in-situpolymerization discussed below. The isolation walls 20 can be aphotoresist or metal, and can be deposited by conventional lithographyprocesses. As shown in FIG. 2A, the walls 20 can form a rectangulararray, with each micro-LED 14 in an individual recess 22 defined by thewalls 20. Other array geometries, e.g., hexagonal or offset rectangulararrays, are also possible. Possible processes for back-plane integrationand isolation wall formation are discussed in more detail below.

The walls can have a height H of about 3 to 20 μm. The walls can have awidth W of about 2 to 10 μm. The height H can be greater than the widthW, e.g., the walls can have an aspect ratio of 1.5:1 to 5:1. The heightH of the wall is sufficient to block light from one micro-LED fromreaching an adjacent micro-LED.

FIGS. 3A-3H illustrate a method of selectively forming color conversionagent (CCA) layers over a micro-LED array. Initially, as shown in FIG.3A, a first photo-curable fluid 30 a is deposited over the array ofmicro-LEDs 14 that are already integrated with the backplane circuitry.The first photo-curable fluid 30 a can have a depth D greater than aheight H of the isolation walls 20.

Referring to FIG. 4A, the first photo-curable fluid 30 a includes atleast cross-linkable groups 32, a photo-initiator 34 to triggerpolymerization under illumination of a wavelength corresponding to theemission of the micro-LEDs 14, and color conversion agents 36 a.

The cross-linkable groups 32 will increase the viscosity of the fluid 30a when subjected to polymerization, e.g., the fluid 30 a can besolidified or form gel-like network structures. The cross-linkablegroups 32 can be provided by monomers that form a polymer when cured,e.g., acrylate, methacrylate and acrylamide. The cross-linkable groups32 can be provided by a negative photoresist, e.g., SU-8 photoresist.

Examples of the photo-initiator 34 include Irgacure 184, Irgacure 819,Darocur 1173, Darocur 4265, Dacocur TPO, Omnicat 250 and Omnicat 550.

The color conversion agents 36 a is a material that can convert theshorter wavelength light from the micro-LED 14 into longer wavelengthlight corresponding to one of the three colors. In the exampleillustrated by FIGS. 3A-3H, the color conversion agent 36 converts theUV light from the micro-LED 14 into blue light. The color conversionagent 36 can include quantum dots, nanostructures, organic or inorganicflorescence molecules, or other suitable materials.

Optionally, the first photo-curable fluid 30 a can include a solvent 37,e.g., water, ethanol, toluene or methylethylketone, or a combinationthereof. The solvent can be organic or inorganic. The solvent can beselected to provide a desired surface tension and/or viscosity for thefirst photo-curable fluid 30 a. The solvent can also improve chemicalstability of the other components.

Optionally, the first photo-curable fluid 30 a can include one or moreother functional ingredients 38. As one example, the functionalingredients can affect the optical properties of the color conversionlayer. For example, the functional ingredients can includenano-particles with a sufficiently high index of refraction that thecolor conversion layer functions as an optical layer that adjusts theoptical path of the output light, e.g., provides a microlens.Alternately or in addition, the nano-particles can have an index ofrefraction selected such that the color conversion layer functions as anoptical layer that reduces total reflection loss, thereby improvinglight extraction. As another example, the functional ingredients can bea surfactant to adjust the surface tension of the fluid 30 a.

Returning to FIG. 3A, the first photo-curable fluid 30 a can bedeposited on the display over the micro-LED array by a spin-on, dipping,spray-on, or inkjet process. An inkjet process can be more efficient inconsumption of the first photo-curable fluid 30 a.

Next, as shown in FIG. 3B, the circuitry of the backplane 16 is used toselectively activate a first plurality of micro-LEDs 14 a. This firstplurality of micro-LEDs 14 a correspond to the sub-pixels of a firstcolor. In particular, the first plurality of micro-LEDs 14 a correspondto the sub-pixels for the color of light to be generated by the colorconversion components in the photo-curable fluid 30 a. For example,assuming the color conversion component in the fluid 30 a will convertlight from the micro-LED 14 into blue light, then only those micro-LEDs14 a that correspond to blue sub-pixels are turned on. Because themicro-LED array is already integrated with the backplane circuitry 18,power can be supplied to the micro-LED display 10 and control signalscan be applied by a microprocessor to selectively turn on the micro-LEDs14 a.

Referring to FIGS. 3B and 3C, activation of the first plurality ofmicro-LEDs 14 a generates illumination A (see FIG. 3B) which causesin-situ curing of the first photo-curable fluid 30 a to form a firstsolidified color conversion layer 40 a (see FIG. 3C) over each activatedmicro-LED 14 a. In short, the fluid 30 a is cured to form colorconversion layers 40 a, but only on the selected micro-LEDs 14 a. Forexample, a color conversion layer 40 a for converting to blue light canbe formed on each micro-LED 14 a.

In some implementations, the curing is a self-limiting process. Forexample, illumination, e.g., UV illumination, from the micro-LEDs 14 acan have a limited penetration depth into the photo-curable fluid 30 a.As such, although FIG. 3B illustrates the illumination A reaching thesurface of the photo-curable fluid 30 a, this is not necessary. In someimplementations, the illumination from the selected micro-LEDs 14 a doesnot reach the other micro-LEDs 14 b, 14 c. In this circumstance, theisolation walls 20 may not be necessary.

However, if the spacing between the micro-LEDs 14 is sufficiently small,isolation walls 20 can affirmatively block illumination A from theselected micro-LED 14 a from reaching the area over the other micro-LEDsthat would be within the penetration depth of the illumination fromthose other micro-LEDs. Isolation walls 20 can also be included, e.g.,simply as insurance against illumination reaching the area over theother micro-LEDs.

The driving current and drive time for the first plurality of micro-LEDs14 a can be selected for appropriate photon dosage for the photo-curablefluid 30 a. The power per subpixel for curing the fluid 30 a is notnecessarily the same as the power per subpixel in a display mode of themicro-LED display 10. For example, the power per subpixel for the curingmode can be higher than the power per subpixel for the display mode.

Referring to FIG. 3D, when curing is complete and the first solidifiedcolor conversion layer 40 a is formed, the residual uncured firstphoto-curable fluid is removed from the display 10. This leaves theother micro-LEDs 14 b, 14 c, exposed for the next deposition steps. Insome implementations, the uncured first photo-curable fluid 30 a issimply rinsed from the display with a solvent, e.g., water, ethanol,toluene or methylethylketone, or a combination thereof. If thephoto-curable fluid 30 a includes a negative photoresist, then therinsing fluid can include a photoresist developer for the photoresist.

Referring to FIGS. 3E and 4B, the treatment described above with respectto FIGS. 3A-3D is repeated, but with a second photo-curable fluid 30 band activation of a second plurality of micro-LEDs 14 b. After rinsing,a second color conversion layer 40 b is formed over each of the secondplurality of micro-LEDs 14 b.

The second photo-curable fluid 30 b is similar to the firstphoto-curable fluid 30 a, but includes color conversion agents 36 b toconvert the shorter wavelength light from the micro-LEDs 14 into longerwavelength light of a different second color. The second color can be,for example, green.

The second plurality of micro-LEDs 14 b correspond to the sub-pixels ofa second color. In particular, the second plurality of micro-LEDs 14 bcorrespond to the sub-pixels for the color of light to be generated bythe color conversion components in the second photo-curable fluid 30 b.For example, assuming the color conversion component in the fluid 30 bwill convert light from the micro-LED 14 into green light, then onlythose micro-LEDs 14 b that correspond to green sub-pixels are turned on.

Referring to FIGS. 3F and 4C, optionally the treatment described abovewith respect to FIGS. 3A-3D is repeated yet again, but with a thirdphoto-curable fluid 30 c and activation of a third plurality ofmicro-LEDs 14 c. After rinsing, a third color conversion layer 40 c isformed over each of the third plurality of micro-LEDs 14 c.

The third photo-curable fluid 30 c is similar to the first photo-curablefluid 30 a, but includes color conversion agents 36 c to convert theshorter wavelength light from the micro-LEDs 14 into longer wavelengthlight of a different third color. The third color can be, for example,red.

The third plurality of micro-LEDs 14 c correspond to the sub-pixels of athird color. In particular, the third plurality of micro-LEDs 14 ccorrespond to the sub-pixels for the color of light to be generated bythe color conversion components in the third photo-curable fluid 30 c.For example, assuming the color conversion component in the fluid 30 cwill convert light from the micro-LED 14 into red light, then only thosemicro-LEDs 14 c that correspond to red sub-pixels are turned on.

In this specific example illustrated in FIGS. 3A-3F, color conversionlayers 40 a, 40 b, 40 c are deposited for each color sub-pixel. This isneeded, e.g., when the micro-LEDs generate ultraviolet light.

However, the micro-LEDs 14 could generate blue light instead of UVlight. In this case, the coating of the display 10 by a photo-curablefluid containing blue color conversion agents can be skipped, and theprocess can be performed using the photo-curable fluids for the greenand red subpixels. One plurality of micro-LEDs is left without a colorconversion layer, e.g., as shown in FIG. 3E. The process shown by FIG.3F is not performed. For example, the first photo-curable fluid 30 acould include green CCAs and the first plurality 14 a of micro-LEDscould correspond to the green subpixels, and the second photo-curablefluid 30 b could include red CCAs and the second plurality 14 b ofmicro-LEDs could correspond to the red subpixels.

Assuming that the fluids 30 a, 30 b, 30 c included a solvent, somesolvent may be trapped in the color conversion layers 40 a, 40 b, 40 c.Referring to FIG. 3G, this solvent can be evaporated, e.g., by exposingthe micro-LED array to heat, such as by IR lamps. Evaporation of thesolvent from the color conversion layers 40 a, 40 b, 40 c can result inshrinking of the layers so that the final layers are thinner.

Removal of the solvent and shrinking of the color conversion layers 40a, 40 b, 40 c can increase concentration of color conversion agents,e.g., quantum dots, thus providing higher color conversion efficiency.On the other hand, including a solvent permits more flexibility in thechemical formulation of the other components of the photo-curablefluids, e.g., in the color conversion agents or cross-linkablecomponents.

Optionally, as shown in FIG. 3H, a UV blocking layer 50 can be depositedon top of all of the micro-LEDs 14. The UV blocking layer 50 can blockUV light that is not absorbed by the color conversion layers 40. The UVblocking layer 50 can be a Bragg reflector, or can simply be a materialthat is selectively absorptive to UV light. A Bragg reflector canreflect UV light back toward the micro-LEDs 14, thus increasing energyefficiency.

FIGS. 5A-5E illustrate a method of fabricating a micro-LED array andisolation walls on a backplane. Referring to FIG. 5A, the process startswith the wafer 100 that will provide the micro-LED array. The wafer 100includes a substrate 102, e.g., a silicon or a sapphire wafer, on whichare disposed a first semiconductor layer 104 having a first doping, anactive layer 106, and a second semiconductor layer 108 having a secondopposite doping. For example, the first semiconductor layer 104 can bean n-doped gallium nitride (n-GaN) layer, the active layer 106 can be amultiple quantum well (MQW) layer 106, and the second semiconductorlayer 107 can be an p-doped gallium nitride (p-GaN) layer 108.

Referring to FIG. 5B, the wafer 100 is etched to divide the layers 104,106, 108 into individual micro-LEDs 14, including the first, second andthird plurality of micro-LEDs 14 a, 14 b, 14 c that correspond to thefirst, second and third colors. In addition, conductive contacts 110 canbe deposited. For example, a p-contact 110 a and an n-contact 110 b canbe deposited onto the n-GaN layer 104 and p-GaN layer 108, respectively.

Similarly, the backplane 16 is fabricated to include the circuitry 18,as well as electrical contacts 120. The electrical contacts 120 caninclude first contacts 120 a, e.g., drive contacts, and second contacts120 b, e.g., ground contacts.

Referring to FIG. 5C, the micro-LED wafer 100 is aligned and placed incontact with the backplane 16. For example, the first contacts 110 a cancontact the first contacts 120 a, and the second contacts 110 b cancontact the second contacts 120 b. The micro-LED wafer 100 could belowered into contact with the backplane, or vice-versa.

Next, referring to FIG. 5D, the substrate 102 is removed. For example, asilicon substrate can be removed by polishing away the substrate 102,e.g., by chemical mechanical polishing. As another example, a sapphiresubstrate can be removed by a laser liftoff process.

Finally, referring to FIG. 5E, the isolation walls 20 are formed on thebackplane 16 (to which the micro-LEDs 14 are already attached). Theisolation walls can be formed by a conventional process such asdeposition of photoresist, patterning of the photoresist byphotolithography, and development to remove the portions of thephotoresist corresponding to the recesses 22. The resulting structurecan then be used as the display 10 for the processed described for FIGS.3A-3H.

FIGS. 6A-6D illustrate another method of fabricating a micro-LED arrayand isolation walls on a backplane. This process can be similar to theprocess discussed above for FIGS. 5A-5E, except as noted below.

Referring to FIG. 6A, the process starts similarly to the processdescribed above, with the wafer 100 that will provide the micro-LEDarray and the backplane 16.

Referring to FIG. 6B, the isolation walls 20 are formed on the backplane16 (to which the micro-LEDs 14 are not yet attached).

In addition, the wafer 100 is etched to divide the layers 104, 106, 108into individual micro-LEDs 14, including the first, second and thirdplurality of micro-LEDs 14 a, 14 b, 14 c. However, the recesses 130formed by this etching process are sufficiently deep to accommodate theisolation walls 20. For example, the etching can continue so that therecesses 130 extend into the substrate 102.

Next, as shown in FIG. 6C, the micro-LED wafer 100 is aligned and placedin contact with the backplane 16 (or vice-versa). The isolation walls 20fit into the recesses 130. In addition, the contacts 110 of themicro-LEDs are electrically connected to the contacts 120 of thebackplane 16.

Finally, referring to FIG. 6D, the substrate 102 is removed. This leavesthe micro-LEDs 14 and isolation walls 20 on the backplane 16. Theresulting structure can then be used as the display 10 for the processeddescribed for FIGS. 3A-3H.

Terms of positioning, such as vertical and lateral, have been used.However, it should be understood that such terms refer to relativepositioning, not absolute positioning with respect to gravity. Forexample, laterally is a direction parallel to a substrate surface,whereas vertically is a direction normal to the substrate surface.

It will be appreciated to those skilled in the art that the precedingexamples are exemplary and not limiting. For example:

-   -   Although the above description focuses on micro-LEDs, the        techniques can be applied to other displays with other types of        light emitting diodes, particularly displays with other        micro-scale light emitting diodes, e.g., LEDs less than about 10        microns across.    -   Although the above description assumes that the order in which        the color conversion layers are formed is blue, then green, then        red, other orders are possible, e.g., blue, then red, then        green. In addition, other colors are possible, e.g., orange and        yellow.

It will be understood that various modifications may be made withoutdeparting from the spirit and scope of the present disclosure.

What is claimed is:
 1. A method of fabricating a multi-color display,comprising: dispensing a first photo-curable fluid over a display havinga backplane, an array of light emitting diodes electrically integratedwith backplane circuitry of the backplane, and a plurality of isolationwalls formed on the backplane between adjacent light emitting diodes ofthe array of light emitting diodes with the isolations walls spacedapart from the light emitting diodes and extending above the lightemitting diodes, wherein the first photo-curable fluid includes a firstcolor conversion agent; activating a first plurality of light emittingdiodes in the array of light emitting diodes to illuminate and cure thefirst photo-curable fluid below the tops of the isolation walls to forma first color conversion layer over each of the first plurality of lightemitting diodes to convert light from the first plurality of lightemitting diodes to light of a first color; removing an uncured remainderof the first photo-curable fluid such that a top surface of the firstcolor conversion layer remaining on the display is below the tops of theisolation walls; thereafter dispensing a second photo-curable fluid overthe display, the second photo-curable fluid including a second colorconversion agent; activating a second plurality of light emitting diodesin the array of light emitting diodes to illuminate and cure a portionof the second photo-curable fluid below the tops of the isolation wallsto form a second color conversion layer over each of the secondplurality of light emitting diodes to convert light from the secondplurality of light emitting diodes to light of a different second color;and removing an uncured remainder of the second photo-curable fluid suchthat a top surface of the second color conversion layer remaining on thedisplay is below the tops of the isolation walls.
 2. The method of claim1, further comprising: dispensing a third photo-curable fluid over thedisplay, the third photo-curable fluid including a third colorconversion agent; activating a third plurality of light emitting diodesin the array of light emitting diodes to illuminate and cure the thirdphoto-curable fluid to form a third color conversion layer over each ofthe third plurality of light emitting diodes to convert light from thethird plurality of light emitting diodes to light of a different thirdcolor; and removing an uncured remainder of the third photo-curablefluid.
 3. The method of claim 2, wherein the first color, second colorand third color are selected from blue, green and red.
 4. The method ofclaim 3, wherein the first color is blue, the second color is green, andthe third color is red.
 5. The method of claim 2, wherein light emittingdiodes of the array of light emitting diodes are configured to generateultraviolet light.
 6. The method of claim 1, wherein the array of lightemitting diodes include a third plurality of light emitting diodes, andlight emitting diodes of the array of light emitting diodes areconfigured to generate light of a different third color.
 7. The methodof claim 6, wherein no color conversion layer is formed over the thirdplurality of light emitting diodes.
 8. The method of claim 6, whereinthe light emitting diodes of the array of light emitting diodes areconfigured to generate blue or violet light.
 9. The method of claim 8,wherein the first color and second color are selected from green andred.
 10. The method of claim 9, wherein the first color is green and thesecond color is red.
 11. The method of claim 1, wherein dispensing thefirst photo-curable fluid and dispensing the second photo-curable fluidincludes one or more of a spin-on, dipping, spray-on, or inkjet process.12. The method of claim 11, wherein dispensing the first photo-curablefluid and dispensing the second photo-curable fluid includes inkjettingthe first photo-curable fluid and the second photo-curable fluid. 13.The method of claim 1, wherein removing the uncured remainder of thefirst photo-curable fluid and the second photo-curable fluid includesone or more of rinsing and dissolving.
 14. The method of claim 1,wherein during activation of the first plurality of light emittingdiodes, the isolation walls block illumination from the first pluralityof light emitting diodes from reaching the second plurality of lightemitting diodes.
 15. The method of claim 14, wherein the isolation wallscomprise a photoresist.
 16. The method of claim 1, wherein at least oneof the first photo-curable fluid and the second photo-curable fluidincluding a solvent, and the method further comprises evaporating thesolvent.
 17. The method of claim 1, comprising forming a ultravioletblocking layer over the array of light emitting diodes.
 18. The methodof claim 1, wherein light emitting diodes of the array of light emittingdiodes are micro-LEDs.
 19. The method of claim 1, wherein dispensing thefirst photo-curable fluid fills gaps between the light emitting diodesand the isolation walls.
 20. The method of claim 1, wherein theisolation walls comprise a photoresist that extends to the backplane.21. The method of claim 1, wherein the first photo-curable fluid and thesecond photo-curable fluid comprise quantum dots.
 22. A method offabricating a multi-color display, comprising: dispensing a firstphoto-curable fluid over a display having a backplane,_ and an array oflight emitting diodes electrically integrated with backplane circuitryof the backplane, and a plurality of isolation walls formed on thebackplane between adjacent light emitting diodes of the array of lightemitting diodes with the isolations walls spaced apart from the lightemitting diodes and extending above the light emitting diodes, whereinthe first photo-curable fluid including a first color conversion agent;activating a first plurality of light emitting diodes in the array oflight emitting diodes to illuminate and cure the first photo-curablefluid below the tops of the isolation walls to form a first colorconversion layer over each of the first plurality of light emittingdiodes to convert light from the first plurality of light emittingdiodes to light of a first color; removing an uncured remainder of thefirst photo-curable fluid such that a top surface of the first colorconversion layer remaining on the display is below the tops of theisolation walls; thereafter dispensing a second photo-curable fluid overthe display, the second photo-curable fluid including a second colorconversion agent; activating a second plurality of light emitting diodesin the array of light emitting diodes to illuminate and cure the secondphoto-curable fluid below the tops of the isolation walls to form asecond color conversion layer over each of the second plurality of lightemitting diodes to convert light from the second plurality of lightemitting diodes to light of a different second color; removing anuncured remainder of the second photo-curable fluid such that a topsurface of the second color conversion layer remaining on the display isbelow the tops of the isolation walls; thereafter dispensing a thirdphoto-curable fluid over the display, the third photo-curable fluidincluding a third color conversion agent; activating a third pluralityof light emitting diodes in the array of light emitting diodes toilluminate and cure the third photo-curable fluid below the tops of theisolation walls to form a third color conversion layer over each of thethird plurality of light emitting diodes to convert light from the thirdplurality of light emitting diodes to light of a different third color;and removing an uncured remainder of the third photo-curable fluid suchthat a top surface of the third color conversion layer remaining on thedisplay is below the tops of the isolation walls, wherein the firstcolor, second color and third color are selected from blue, green andred.